1. Field of the Invention
The invention relates to a noise reducing apparatus, particularly to a noise reducing apparatus comprising an interfering type hollow body for reducing noise by interfering an incident sound from a sound source.
2. Related Art Statement
Hitherto, the level of noise radiated from a sound source is generally reduced by absorbing and insulating the noise in such a manner as shown in FIG. 12 wherein the sound source 3 such as an electric motor is surrounded by a shield construction 2 provided with a sound absorbing materials 1 on the inner wall thereof.
However, such a conventional sound absorbing shield construction as shown in FIG. 12 has a disadvantage that since actual sound sources such as vehicle engines and electric motors generate heat as well as noise a the same time, the sound absorbing material and the shield construction are required to have a sufficient thermal resistance and the engine and the motor tend get troubles so that the security can not be maintained since the radiation of heat is avoided owing to the closed shield construction.